Dong Hun Hyeon

Novel thin nanocomposite RO membranes for chlorine resistance

Abstract Sulfonated poly(arylene ether sulfone) material containing amino groups (aPES) is successfully synthesized using aromatic substitution polymerization. This material was shown to be a novel thin-film composite (TFC) reverse osmosis (RO) membrane material with high chlorine resistance. Graphene oxide (GO) and aminated graphene oxide (aGO) nanoparticles were also prepared. TFC membranes were prepared using an interfacial polymerization (IP) reaction with trimesoyl chloride (TMC) and amine solution, containing synthesized materials, on a polysulfone (PS) ultrafiltration (UF) support membrane. The synthesized aPES and fabricated TFC RO membranes were characterized by nuclear magnetic resonance spectroscopy and scanning electron microscope. Moreover, RO performances, salt rejection, and water flux were measured using cross-flow cell instrument. The chlorine resistance was evaluated using sodium hypochlorite solution. The membrane fabricated with aPES/GO/aGO was compared with the typical polyamide (PA) ...

Composite membranes based on sulfonated poly(ether ether ketone) and SiO 2 for a vanadium redox flow battery

Organic-inorganic composite membranes were prepared with sulfonated poly(ether ether ketone) (SPEEK) and different amounts of silica to improve chemical stability and vanadium hindrance for a vanadium redox flow battery. The durability of the prepared composite membrane was verified using a self-made dummy cell system and fully charged vanadium cathode half-cell electrolyte, which contained oxidative vanadium ions (VO2+). The prepared composite membranes, with covalent crosslinking between the organic polymer and inorganic particles, resulted in reduced vanadium permeability and enhanced chemical stability. Ion exchange capacity, water uptake, proton conductivity, and vanadium permeability decreased with increasing silica content. Selectivity was defined to consider both permeability and proton conductivity and resulted in a membrane that exhibited both high proton conductivity and low ion permeability simultaneously. The prepared 1 wt% silica composite membrane showed 133-fold higher selectivity compared with that of a Nafion112 membrane. After the stability test, the composite membrane showed little change compared to the membrane before the stability test, which confirmed the commercial prospect of SPEEK/SiO2 composite membrane for a vanadium redox flow battery.

Heat Sink Measurement of Liquid Fuel for High Speed Aircraft Cooling

For hypersonic aircraft, increase of flight speeds causes heat loads that are from aerodynamic heat and engine heat. The heat loads could lead structural change of aircrafts component and malfunctioning. Endothermic fuels are liquid hydrocarbon fuels which are able to absorb the heat loads by undergoing endothermic reactions, such as thermal and catalytic cracking. In this study, methylcyclohexane was selected as a model endothermic fuel and experiments on endothermic properties were implemented. To improve heat of endothermic reaction, we applied zeolites and confirmed that HZSM-5 was the best catalyst for the catalytic performance. The objective is to investigate catalyti c effects for heat sink improvement. The catalyst could be applied to system that use kerosene fuel as endothermic fuel.

Improvement of Heat of Reaction of Jet Fuel Using Pore Structure Controlled Zeolite Catalyst

In hypersonic aircraft, increase of aerodynamic heat and engine heat leads heat loads in airframe. It could lead structural change of aircraft’s component and malfunctioning. Endothermic fuels are liquid hydrocarbon fuels which are able to absorb the heat load by undergoing endothermic reactions. In this study, exo-tetrahydrodicyclopentadiene was selected as a model endothermic fuel and experiments on endothermic properties were investigated with pore structure controlled zeolite catalyst using metal deposition. We secured the catalyst that had better endothermic performance than commercial catalyst. The object of this study is inspect catalyst properties which have effect on heat absorption improvement. Synthetic catalyst could be applied to system that use exo-THDCP as endothermic fuel instead of other commercial catalyst.